Conventional bicycle frames, as illustrated for example in FIG. 13 generally have a one-piece straight seat tube. Bicycle frames with a one-piece seat tube having a curved portion are also known in the art, as illustrated for example in U.S. Pat. No. 5,957,473 to Lawwill and U.S. Pat. No. 4,900,050 to Bishop et al.
It has been found advantageous to establish an aerodynamic shielding on the rear wheel of a bicycle, especially on the upper portion. Attempts to achieve this goal have been made by constructing bicycle frames with a straight seat tube having a recessed curved section. Unfortunately, this design does not allow for a full shielding of the upper portion of the rear wheel.
Trimble in U.S. Pat. Nos. Re. 33,295; 4,941,674; and 4,982,975 discloses a bicycle frame made of composite material. The frame comprises a seat tube having a curved section which is cut into a one-piece straight seat tube. Such seat tube is also illustrated in FIGS. 1(a) and 1(b). The resulted design of the bicycle frame according to Trimble is that of a traditional “double diamond” frame, which has two open triangles with a common side. The curved section of Trimble's seat tube does not allow, however for a full coverage of the upper portion of the rear wheel and thus an optimal aerodynamic shielding is not achieved.
Therefore, there remains a need for a bicycle frame allowing for a maximum aerodynamic shielding and reduced aerodynamic drag. There is also a need for an aerodynamic frame having a brake which is removably attached therefrom without reducing the aerodynamic efficiency of the frame, or its strength or stiffness. Indeed, in frames with recessed curved cutouts it becomes very difficult to attach a brake of conventional design because access to the rear of the brake is required to affix it. A large gap must therefore be left around the back of the brake for access to attach and tighten the brake to the frame. This large gap reduces the aerodynamic efficiency of the frame. In other designs, access holes are provided in the frame for attachment of the brake thereto. This results in adding weight as well as costs, and the stiffness and structural integrity of the frame are reduced.